Visual Field Defects in Glaucoma
Global Incidence of Glaucoma
According to the World Health Organization, glaucoma is the second leading cause of blindness globally after cataracts. What is this condition and what are the visual field defects in glaucoma?
Glaucoma is a condition affecting the eyes. The WHO estimates that it is responsible for 5.2 million cases of blindness worldwide – approximately 15 percent of all cases of blindness. The term glaucoma is applied to a group of illnesses that produce damage to a person’s optic nerve. The optic nerve is responsible for transporting signals produced in the eye to the visual cortex of the brain where they are interpreted.
Glaucoma is usually associated with raised intraocular pressure and it is this which normally damages the optic nerve and results in vision impairment in sufferers. Glaucoma is a gradual disease where impairment of vision occurs slowly, over time at a rate that is hardly discernible by the patient until loss of vision becomes gross.
There are two types of glaucoma known as primary open-angle glaucoma and angle closure glaucoma. In secondary glaucoma, the condition is caused by another condition which results in damage to the optic nerve due to increased intraocular pressure. A secondary glaucoma can result in either type of the condition.
The most common type of glaucoma is primary open-angle glaucoma. The condition has no specific symptoms other than a gradual deterioration of vision. In the advanced stages of the condition, the patient may suffer from tunnel vision (where lateral vision is impaired). Indeed, loss of peripheral vision may be the first symptom that a patient becomes aware of, however, the damage sustained by that time is irreversible.
It is estimated that up to half of all people with this type of glaucoma will be unaware that they are suffering from the condition. In contrast, angle closure glaucoma is associated with severe eye pain which may cause vomiting and nausea. There is a sudden onset of visual disturbance which will be worse in low-light situations. It results in blurred images and light sources may be perceived with halos around them. The eyes of sufferers are usually reddened.
Detection And Treatment
Since the visual field defects associated with the most common type of glaucoma will produce no noticeable signs until the damage is quite advanced, regular, full eye examinations should be scheduled for groups at higher risk of the condition and people over the age of forty. It is recommended that the general population should undergo a full eye examination at least once in a three to five year period. The examination will involve measurement of the intraocular pressure, a painless procedure which involves measurement of the deflection of a stream of air blown towards the patient’s eye.
While there is no cure for glaucoma currently and the damage that has been sustained to a patient’s sight cannot be repaired, it is possible in many cases to prevent further deterioration to sight through medication or surgery. For this reason, it is prudent to get your eyes properly tested at regular intervals.
Glaucoma tends to effects people in later life, although it occurs in younger people as well. In the United States, one in 10 000 babies are born with the condition. The incidence of the disease is higher in African Americans and this population is advised to get their eyes tested for raised intraocular pressure from the age of 40 (this group is 14 to 17 times more likely than Caucasians to develop the condition between the ages of 45 and 65).
As a whole, it is estimated that 4 million Americans suffer from glaucoma, but half of them are unaware of the problem. The total cost of glaucoma to the American economy has been estimated at $1.5 billion per annum.
- WHO Global Impact of Glaucoma: https://www.who.int/blindness/publications/glaucoma/en/
- Glaucoma Research Foundation: https://www.glaucoma.org/learn/glaucoma_facts.php
- Glaucoma, Mayo Clinic: https://www.mayoclinic.com/health/glaucoma/DS00283